Striae distensae (SD) or stretch marks are common and disfiguring dermatologic conditions, which usually arise due to obesity, pregnancy, rapid weight gain or weight loss, certain endocrine conditions, and prolonged use of steroids (1–5). Initially, typical lesions on the abdomen, breasts, thighs, or buttocks present as raised edematous linear plaques or stretched flat (striae rubrae), after which the color fades and turns white and atrophic (striae albae) as a result of local breakdown and reorganization of collagen and elastin bundles (3–6).

According to the domestic and international literature reports, the incidence of stretch marks is approximately 60–90%, and most of them begin to appear around 24 weeks of pregnancy (7, 8). The SD, especially striae albae present with permanent lesions, increasingly cause considerable psycho-social distress, which often leads to a decrease in quality of life (3, 4, 6). The substantial demand for a reliable treatment option is increasing to improve the persistent SD lesions in recent years; there are many treatment modalities used to treat SD, including topical agents, such as tretinoin ointment and olive oil, microneedles, and the energy-based devices, such as RF, pulsed laser, and fractional lasers (9–14).

There is no golden standard in the treatment of SD until now. As reported previously (15–20), both ablative and non-ablative fractional lasers showed certain clinical efficacy in the treatment of striae albae, but most of the studies were clinically retrospective study, without strict design and control. The well-designed controlled study is in urgent need to investigate the efficacy and side effects in the treatment of striae albae with different modalities.

The purpose of our study was to evaluate and compare the clinical efficacy and safety of 10,600 nm ablative CO₂ and 1,550 nm non-ablative Er: glass fractional lasers for the treatment of striae albae by self-controlled studies.

Totally, 27 cases were treated and two cases were lost during follow-up. Totally, 25 patients with striae albae were enrolled in in the final analysis (of which 20 were Fitzpatrick skin type III and five were IV type). The patients ranged in age from 26 to 38 years (mean 32.93 ± 3.71 years), and the duration of striae albae ranged from 1 to 13 years (mean 5.12 ± 2.95 years).

There was no aggravation of stretch marks on both sides treated. The results of the two lasers are shown in Table 1 and Figures 1–5. There was a significant difference in clinical efficacy between the two sides (p = 0.002, p < 0.05) (Figures 1–5 and Table 1).

The self-evaluation of patient satisfaction with striae albae improvement was similar to the picture assessments and is shown in Table 2. The difference in patient satisfaction between the two treatment methods was statistically significant (p = 0.034, p < 0.05) (Table 2).

The SD, especially the striae albae, is therapeutically challenging form of dermal scarring, which causes the significant psycho-social distress and the treatment requirement is increasing in recent years (17, 18). The fractional lasers may be a potential treatment modality for striae albae. The mechanism of fractional laser treatment is based on the theory of fractional photothermolysis (19, 20), and the factional damage of the epidermis and dermis by fractional laser results in the thermal effects promoting the synthesis of new collagen fibers, thereby improving the stretch marks. Gokalp et al. (20) reported 16 patients with SD treated by a 1,550 nm non-ablative fractional laser and followed up for 1 year after the last treatment, with a total effective rate of 81.25%. Another study confirmed that the efficacy of CO₂ fractional laser is more effective than IPL in the treatment of SD (21). For the comparatively deeper effect by fractional CO₂ laser than IPL.

In this study, we performed the comparative study to compare the ablative CO₂ vs. non-ablative fractional 1,550 nm laser for the treatment of striae albae. The previous study showed that the ablative CO₂ fractional laser may provide better efficacy than non-ablative 1,550 nm fractional laser (16), and the treatment interval in this study was only 4 weeks, which seems a bit short for the observation of collagen remodeling. Our study highlights that the 1,550 nm non-ablative fractional laser may have better efficacy in the treatment of striae albae by the blinded evaluation and the patients’ self-satisfaction report. The potential explanation may be due to the different laser settings used in the study. The energy of fractional CO₂ laser was 60–75 mJ (the maximum energy of the system was 115 mJ),while the energy of NFL was 60–80 mJ (the maximum of 120 mJ), which was determined based on our previous experience with these lasers and the therapeutic response and tolerance of the patients. We found that when the fluence of NFL is increased, the effective penetration depth is also increased and more new collagen fiber synthesis and collagen remodeling in the dermis may be induced. Furthermore, when the fluence is high enough, the damage to the epidermis could also be observed. The concept of non-ablative and ablative comparatively depends on the laser settings. On the other hand, the higher energy of NFL with longer pulse duration leads to more pain, which is the main complaint of NFL in the treatment of striae albae.

The contents of melanin are relatively high in Asian skin, and the incidence of PIH after laser treatment is higher than that of Europeans and Americans (22). Of the 25 patients in our study, 20 were Fitzpatrick skin type III and five were type IV. The results of this study showed that the probabilities of PIH (24%) on the CO₂ fractional laser treatment side were higher than those of 1,550 nm Er: glass fractional laser treatment side (8%), but neither of them had permanent pigmentation changes.

Our study found that the non-ablative fractional 1,550 nm laser may be more effective in the treatment of striae albae. However, the cases involved in the study and the follow-up time are limited. Further study to compare different laser settings for collagen remodeling with lasers is required to confirm our findings.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Ethics Committee of Shandong Provincial Hospital for Skin Diseases. The patients/participants provided their written informed consent to participate in this study.

HL designed the study. YFL, YL, and MW colleceted the enrolled cases. XG and XL followed the cases. YFL and HL prepared the manuscript. All authors contributed to the article and approved the submitted version.